Conduct Direct Message Conversations
In Slack, direct messages, also called DMs, are used for one-on-one conversations and for group conversations with up to nine people total.
Unlike a channel, which has a descriptive name—like #acct-general or #edit-general—the title of a DM conversation in the sidebar is based on the people with whom you’re conversing—like Tonya, Adam—and always remains the same. DM conversations are analogous to instant messaging or group messaging. In fact, these conversations can replace your use of an instant-messaging (IM) service, such as SMS, WhatsApp, iMessage, or Google Hangouts.
Slack suggests, and I agree, that group DMs are best suited for brief interactions among a static group of people. If you want to add or remove people, a channel works better (see Work with Channels).
All DMs may be viewed and searched only by the participants, a fact that may be incidental for some interactions but essential for others—in fact, only members can even see that a DM conversation exists. If privacy is paramount, you may prefer to set up a private channel, which offers more flexibility; for details, see the sidebar DM Conversations vs. Private Channels, earlier.
Start a DM Conversation
You can start a DM conversation in a lot of ways, but the most obvious one is to click or tap the Add 
button next to Direct Messages in the main sidebar to open the Direct Messages dialog. (Recall that, in iOS, you tap the Slack 
icon, and in Android, the workspace icon, to view the main sidebar.) For additional methods, see the sidebar More Ways to Start a Direct Message.
With the Direct Messages dialog (in desktop and web apps) or New Conversation view (in mobile apps) open:
Desktop and web apps: Select, type, arrow up or down, or use autocomplete to add people to the “Find or start a conversation” field. Click Go when you’re ready to start (Figure 79).
Figure 79: Select participants and click Go. Mobile apps: For each person you want to add, tap the circle next to their name so it fills. Tap Next to begin the conversation.
Slack opens the message list to your new DM conversation. The top of the list displays information about it, noting who you’ve included in it. (In desktop and mobile apps, Slack tells you it’s the start of “your direct message history with” the participants; in mobile, “This is the very beginning of your group message.”)
In the desktop and web apps—if your conversation includes at least three people—Slack also provides an Edit link that lets you set notifications (Figure 80). These settings control how you’re informed when people post in the conversation. I cover these preferences in full in Set Notification Preferences.
Slack doesn’t otherwise strongly alert you when someone has started a conversation in which you’re involved. It shows the conversation in the Direct Messages section of the sidebar in bold type and displays the number of unread messages next to it.
Continue a DM Conversation
Just like a channel, you click or tap the name of a DM conversation in the sidebar to open its message list. Also, just like a channel, a DM conversation can be starred, hidden, or muted (see Star a Channel or Conversation and Control Slack Notifications on Your Device).
However, once you switch out of a DM conversation, Slack gives you cues about what you’ve missed. But may need some help to find the conversation and resume it.
See Unread Messages
The number of unread direct messages appears in a badge to the right of the DM conversation name in the sidebar.
If a number appears to the left of a DM conversation’s name in the main sidebar (in all apps except Android), that number indicates how many people besides you belong to the conversation. It shows “3” if there are four members, for instance. For one-on-one DMs, instead of a number, Slack displays a presence indicator, such as the sleep 
icon. (See Make Your Presence Known for more about these icons.)
If Slack considers you to be inactive in any app, the system notifies you of every direct message. If you are active, but aren’t in the conversation in which a direct message is posted, you may get notified of that message, too. (You can disable or override these in various ways; see Workspace-Wide Notifications for details.)
Look for Older DM Conversations
If you have a lot of DM conversations, those that have been inactive for the longest disappear off bottom of the Direct Messages list in the sidebar. If this is a bother, star important conversations to make them persist.
If you can’t easily locate an existing set of DMs in the sidebar, try one of these techniques:
Direct Messages dialog: Open the Direct Messages dialog, either by clicking or tapping the Add
button next to Direct Messages in the sidebar or using a method described in the sidebar More Ways to Start a Direct Message. Notice that this dialog lists every DM conversation you’ve had from newest to oldest (Figure 81). Locate and then select the conversation.
Figure 81: Find your DM conversations. Desktop and web apps: Bring up the Quick Switcher and start typing the name or handle of a person in the DM conversation to find matches. Click the conversation name once you find it.
Mobile apps: In the “Jump to” field at the top of the main sidebar, type the name or handle of a person in the DM conversation to find matches. When the conversation appears in the results list, tap it.
Change Participants in a Group DM
If you’re messaging with just one other person, you can’t add anyone else; with two or more, you can change the participants. But it’s not like in a private channel, where adding or removing lets you keep the channel name and, optionally, its history. If you add or remove even just one person, it’s really a new conversation that lacks any continuity from the old one.
The new set of participants have no access to the old messages from within the new conversation. The old conversation remains, but only the participants in that conversation can switch back to it or search to access its contents.
To change the people in a conversation:
Desktop and web apps: Click the Conversation Settings
button and choose “Invite another member” to see the Direct Messages dialog, where you can add people in the field at the top. You can also, contrary to the menu label, remove people: just click the x in a person’s tile at the top of the dialog. Slack warns you that a new conversation will be created.Mobile apps: Tap the list of names at the top of the message list, and tap Add Someone. On the New Conversation screen, tap the selection circles to add or remove people.
End a DM Conversation
Channels can be archived, but DM conversations can seemingly last forever. If you don’t want to see a conversation in the sidebar, you can hover over it in a desktop or web app and click the x that appears to the right of its name. In a mobile app, tap the conversation name, tap the participants name at the top of the messaging view, and finally tap Close Conversation.
The conversation’s messages aren’t deleted, though, and the conversation isn’t wiped from Slack. As soon as anyone in the conversation posts a new message to it, the conversation re-appears in your sidebar and you get an alert (if you have notifications configured to show direct message activity).
If you’ve hidden a conversation but want to access it, click the Add button adjacent the Direct Messages heading in the sidebar and call it up again, or use an alternative mentioned in the More Ways to Start a Direct Message sidebar.
Talk to Yourself
Slack lets you use DMs to yourself as a means of private conversation. It has two main uses: to store private note and provide a private workspace.
Keep Private Notes
You can use direct messages to store private notes and other information. Everything in this DM conversation becomes searchable, but you’re the only one who sees those search results.
You can do almost anything in a DM conversation with yourself that you can in any other conversation, including applying formatting to messages.
Test a Message
I often use my DM conversation as a test bed. For instance, when I compose a post, I start in my DM conversation, work on it while sharing it only there, and only once it’s refined do I share it with a channel or an additional conversation.
You can also upload files to your own DM conversation to see how they look in Slack or to make sure they appear in the message list as expected, before you upload them to another conversation or to a channel.